1. Field of the Invention
This invention relates generally to anti-theft devices for manually powered swivel-wheel shopping carts, and particularly to an apparatus for use in controlling or inhibiting the unauthorized use and removal of these swivel-wheel shopping carts from a specified or designated area. The invention specifically relates to a method and apparatus for sensing and measuring the distance a swivel-wheel shopping cart travels after a triggering event has occurred. Should the cart move beyond its preprogrammed authorized distance, a braking mechanism is engaged to inhibit the free rotation of one or more of the cart's wheels, thereby interfering with further movement of the cart.
2. Brief Description of the Prior Art
Presently, there are thousands of grocery stores, shopping plazas, hardware and gardening centers that provide their customers with the convenience of having a shopping cart available to transport goods to and from their premises. Once the customer is finished with the cart, it is typically returned to a designated area or simply abandoned in the store's parking lot. Due to the number of shopping carts used during the course of a business day by one of these stores or supermarkets, it is difficult to account for each and every cart used. Shopping carts are often stolen or borrowed for some otherwise innocent purpose. However, regardless of the purpose for removal, once a cart is removed from a store's premises, it is almost never returned.
The cart owners are justifiably concerned about the unauthorized use and theft of their shopping carts since the average shopping cart costs approximately $120.00. Due to the expense, as well as the frequency of theft, lucrative businesses have been created specializing in shopping cart recovery. However, industry statistics have shown that these firms are only able to recover approximately thirty percent of all the carts stolen or removed during the course of a calendar year. This means that out of a million carts stolen each year there are over 600,000 carts that are never recovered. By adding costs associated with both replacement and recovery to the day-to-day operations of these business, an anti-theft system that tends to prevent a shopping cart from ever leaving a store's premises will save the retail industry in excess of $60 million per year.
Previous methods have been devised in an attempt to prevent shopping carts from being removed or stolen. One such system includes installation of physical barriers along the perimeter of a parking area to prevent the user from pushing the cart into the parking area. However, such barriers are impractical since it is desirable to allow a customer to take the cart to his car for the loading or unloading of his goods. Other anti-theft devices or systems designed for shopping carts are configured with some type of wheel-locking mechanism that is triggered by either a timer, or by a magnetic field with a fixed frequency, when the shopping cart passes through it. Most of these anti-theft systems require extensive modifications to the shopping cart and the wheel so that the locking mechanism works properly. An example of this type of system is disclosed in U.S. Pat. No. 2,964,140 granted December 1960 to M. N. Berezny. This anti-theft system employs an electromagnetically actuated, pin-directed braking mechanism which can be installed in place of one or more of the cart's wheels. Upon activation, the system forces a horizontally positioned pin into an aperture in the wheel, preventing the wheel from turning or moving any farther. The disclosed device incorporates a fixed magnetic field as a means of activating the brake mechanism at an appropriate time. When the cart passes over a cable that has been either embedded in the concrete about the perimeter of the parking lot to generate a magnetic field, or has been placed in front of the exit of the store, a sensor activates and closes a switch in the control logic of the locking mechanism that, in turn, forces the pin into an available opening in the wheel, impeding its rotation.
Anti-theft devices like the one described above have had a number of problems. Firstly, the devices require that a magnetic cable be installed around the perimeter of the parking lot, or if the magnetic cable is used at the exits of the parking lot, then the lot must be fenced. In any event, neither of these approaches are cost-effective or practical. Secondly, the brake mechanism of the Berezny system is exposed and susceptible to being damaged by a person bent on stealing the cart. Thirdly, this approach requires that the sensory and the braking elements of the system be calibrated and balanced several times a month to operate effectively. If the system is not calibrated or maintained properly, the locking mechanism will not respond properly, thus locking the wheel prematurely.
Another approach is disclosed in U.S. Pat. No. 4,242,668 granted December 1980 to W. Herzog. This apparatus mounts to the front of a cart and uses a latched brake or blocking mechanism which falls down in front of the cart, stopping its forward progress. Like Berezny's system, the latched brake mechanism is activated by a sensor installed on the cart's undercarriage. The sensor detects when the cart has crossed over a magnetic strip placed at an exit of the parking lot. Once again, the principal disadvantage of this anti-theft system lies in the prohibitive expense and complex modification required to install this type of system to the undercarriage of an existing cart. Again, like Berezny, Herzoq leaves the locking device, or mechanism, open to vandalism and damage by a would-be thief.
Still another approach can be found in U.S. Pat. No. 3,652,103, granted in March 1972 to S. P. Higgs. Unlike the other systems described above, this system incorporates a timer to activate a braking mechanism. With this type of system, when the cart leaves the shopping facility, the timer is activated and after a predetermined period of time, the brake mechanism engages, interfering with further movement of the cart. Here, the time period is determined by how much time a customer requires to reach the farthest point of the parking lot plus some contingency for a momentary stop or delay. With this approach, when the timer approaches its limit, it slowly engages the brake making the cart more and more difficult to move. Thus, if a customer is parked at the farthest point in the parking lot, and the braking mechanism engages prematurely, making the cart difficult to push, a great deal of customer annoyance and dissatisfaction results. Furthermore, the expense required to install and maintain an anti-theft system of this type will have a significant impact on the overhead costs associated with a typical retail operation.
Further still, another and somewhat more practical solution is disclosed in U.S. Pat. No. 4,772,880 granted September 1988 to L. W. Goldstein et al. This patent discloses a clamp-on, battery-powered receiver and sensor system that detects when a cart is about to be removed and activates a bolt-on locking mechanism to prevent the cart from leaving a parking lot or prescribed use area. Although easily installed, this type of device is subject to vandalism and removal, thus allowing the cart to be damaged or easily stolen. Like the other systems defined above, this system requires that a set of transmitters be installed around the perimeter of the parking lot and adds substantially to the start-up and maintenance costs to support such a system.
As illustrated by the numerous thefts that occur each and every day, these systems have failed to prevent or even substantially reduce the unauthorized removal of such carts. In addition, these systems tend to be difficult to install and maintain, requiring special equipment and tools to keep the cart in operational condition. More importantly, most of these systems require that expensive components be added to each shopping cart, not to mention the expense required for the equipment that must be installed around the perimeter, or at the exits of a parking lot, in order to operate the system effectively.
Thus, there still exists a substantial need to provide a cart theft deterrent system that is cost-effective to produce, install and maintain.